c l i n i c a l f o l i o s : n a r r a t i v e





A D V E R T I S E M E N T

 

Early Heart Formation: 4

A D V E R T I S E M E N T

   
 

Toward the end of the third week angioblastic cells in the splanchnic layer of mesoderm coalesce and vacuolate to form primitive blood vessels. Two dominant pairs of channels form, one at the rim of the infolding foregut and the other more centrally on either side of the midline. The former come together from cephalad to caudad as the foregut closes and unite to form the primitive heart tube. The latter will form the paired dorsal aortae.     

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Early Heart Formation: 5

A D V E R T I S E M E N T

   
 

The angioblastic tissue on the splanchnic side of the presumptive pericardial cavity is called the cardiogenic plate and will form the heart tubes. Overgrowth of the head fold and infolding of the foregut rotate the pericardial cavity and cardiogenic plate so that the former is ventral and the latter is dorsal.      

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Early Heart Formation: 6

A D V E R T I S E M E N T

   
 

Bilateral fusiform heart tubes form from the cardiogenic plate. The apposed wall of splanchnic mesoderm forming the pericardial cavity (now the dorsal wall) invests the endothelial heart tubes and differentiates into primitive myocardium. By day 22 the heart tubes have united with the dorsal aortae and begin contracting in an antegrade direction and by day 24 early blood elements begin circulating. The myocardium secretes a cushioning layer of cardiac jelly between itself and the endothelial tube. Subsequent migration of epithelial cells will form the epicardium on the heart tubes.     

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This page was last modified on 5/28/1999.